We planned to conduct a study evaluating the efficacy of MI-E in the prevention of extubation failure and mortality in these patients. If no signs of respiratory failure appeared after 120 min of a spontaneous breathing trial, patients will be extubated and randomly allocated after extubation to MI-E group or control group. The clinical follow-up will be as follow: the incidence of extubation failure, the reintubation, the ICU or 28-day survival,90-day survival, ICU length of stay.